The amount of energy we use to manufacture the products we use every day is a significant part of the energy needed to support out lifestyle. As the planet gets more and more populated, can we continue to make manufacturing more efficient, or are thee limits to this?

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A new report by researchers at MIT and elsewhere finds that the global manufacturing sector has made great strides in energy efficiency: The manufacturing of materials such as steel, cement, paper and aluminum has become increasingly streamlined, requiring far less energy than when these processes were first invented.

However, despite more energy-efficient manufacturing, the researchers found that such processes may be approaching their thermodynamic limits: There are increasingly limited options available to make them significantly more efficient. The result, the team observed, is that energy efficiency for many important processes in manufacturing is approaching a plateau.

The researchers looked at how materials manufacturing might meet the energy-reduction targets implied by the Intergovernmental Panel on Climate Change, which has suggested a 50 percent reduction in carbon-dioxide emissions by 2050 as a means of avoiding further climate change. Meanwhile, economists have estimated that global demand for materials will simultaneously double.

To reduce energy use by 50 percent while doubling the output of materials, the team — led by graduate student Sahil Sahni and Tim Gutowski, a professor of mechanical engineering at MIT — studied whether manufacturing processes could improve in efficiency by 75 percent. The researchers identified the five most energy-using materials produced, and outlined scenarios in which further energy may be saved in manufacturing. But even in the most aggressive scenario, the team found it was only able to reduce energy use by about 50 percent — far short of its 75 percent goal.

"What we’re saying is, when you look really big, at global targets for limiting climate change, we think this appears to be beyond what industry can do by itself," says Gutowski, who leads MIT's Environmentally Benign Manufacturing research group. "If industry can’t meet these goals, we may need bigger cuts in other sectors."